Baking and roasting oven

ABSTRACT

Baking and roasting oven which includes a muffle chamber having a top wall, a bottom wall and a lateral wall extending between the top and bottom walls, also has a heating means including a circulating blower for hot air, a blower channel for the hot air circulated by the blower, the blower channel interconnecting respective hot air exhaust and hot air injection openings and injection openings being at an elevation of at least one-fourth the height of the muffle chamber from the bottom wall thereof.

United States Patent 1 [1 11 3,7216% Klement 51 Apr. 17, 1973 BAKING ANDROASTING OVEN [56] References Cited [75]. Inventor: Johann Klement,Traunreut, Ger- UNITEE S TA T ES PATENTS many 3,474,225 10/1969 Leedyv.126 21 A Assignee: Siemens-Electrogemte Ber- THUS X lin and Munich,Germany Primary ExaminerEdward G. Favors [22] Filed: Feb. 9, 1972 App].No.: 224,693

Foreign Application Priority Data Feb. 12, 1971 Germany ..P 21 06 775.4

US. Cl. ..l26/2l A, 219/400 Int, Cl. ..A21b 1/26 Field of Search 126/21,273;

AtzorneyArthur E. Wilfond et a].

[ 5 7 ABSTRACT Baking and roasting oven which includes a muffle chamberhaving a top wall, a bottom wall and a lateral wall extending betweenthe top and bottom walls, also has a heating means including acirculating blower for hot air, a blower channel for the hot aircirculated by the blower, the blower channel interconnecting respectivehot air exhaust and hot air injection openings and injection openingsbeing at an elevation of at least one-fourth the height of the mufflechamber from the bottom wall thereof.

21 Claims, 8 Drawing Figures PATENTEUAPR1 1197s sum 2 OF 2 tion openingsformed in the wall of the muffle chamber.

A baking and roasting oven of this general type is known from BritishPat. No. 1,088,663. The circulating blower which, together with aheating member make up the heating device, serves for effecting aso-called self-cleaning operation in which the muffle chamber is heatedto such a high temperature (over 500C) by circulating hot air thatresidues and impurities which adhere to the inner wall of the mufflechamber automatically become incinerated.

The exhaust openings and injection openings for the circulated hot airare located in the bottom wall of the muffle chamber in the embodimentof the aforementioned British Patent. A consequence of this dispositionof the exhaust and injection openings is that a vertically directed flowof hot air is produced within the muffle chamber during operation of thecirculating blower. The incoming hot air flows from the bottom wall ofthe muffle chamber toward the top wall of the muffle chamber and flowsback therefrom toward the bottom wall, in direction of the exhaustopenings.

It has been found that the heretofore known disposition of the exhaustand injection openings in the wall of the muffle chamber and thevertical flow of the circulating hot air that is associated therewithentail various disadvantages.

First of all, there is the possibility that the previously incineratedresidues will fall off the wall of the muffle chamber, will be suckedinto the circulating blower, and possibly clog the latter. Thiscircumstance is particularly detrimental when the sucked-in residuesadhere to the heating member of the circulating blower and ignitethereon. This can markedly reduce the durability of the heating member.

Usually, the baking and roasting ovens have other heating members inaddition to the heating member for the circulating blower which arecoordinated as upper heat and lower heat for the top and bottom walls,respectively,- of the muffle chamber. When a self-cleaningoperation isperformed, these other heating members cooperate withthe heating memberof the circulating blower. When the flow of circulated hot air isdirected toward the top and bottom walls of the muffle v chamber, it isthen noticeable that these walls detrimentally attain considerablyhigher temperatures than the remaining parts of the muffle chamberbecause they are subjected to a summation of the upper" and lower heats"as well as the heat of the circulated hot air. Of the disadvantageousconsequences of this thermal inequality, there might be noted primarily,the danger that the muffle chamber walls may warp, thereby causingcracking or rupture of the enamel layer, applied thereto for protectionagainst oxidation.

It is accordingly an object of the invention to provide a baking androasting oven of the foregoing type having a heating device whichfunctions especially reliably with respect to the circulating blowerduring the selfcleaning operation and which also affords thermal balanceor equilibrium of the muffle chamber, particularly when an upper andlower heat is provided at the top and bottom wall, respectively, of themuffle chamber.

With the foregoing and other objects in view, there is provided inaccordance with the invention, baking and roasting oven including amuffle chamber having a top wall, a bottom wall and a lateral wallextending between the top and bottom walls, including a heating meanshaving a circulating blower for hot air, a blower channel for the hotair circulated by the blower, the blower channel interconnectingrespective hot air exhaust and hot air injection openings formed in thelateral wall of the muffle chamber, the exhaust and injection openingsbeing at an elevation of at least onefourth the height of the mufflechamber from the bottom wall and the top wall thereof.

In accordance with another feature of the invention, both the exhaustand injection openings are located at the same level.

Thus, in a relatively simple manner, incinerated residues are preventedfrom falling through the exhaust openings into the circulating blowerduring the selfcleaning operation. The residues collect on the bottomwall of the muffle chamber from which the exhaust openings of thecirculating blower are spaced a distance corresponding to at least onefourth of the height of the muffle chamber. The residues that collect onthe bottom wall of the muffle chamber can not be whirled upwardly againthrough the incoming hot air, because the injection openings, accordingto the invention, are also located at a distance from the bottom wallthat corresponds to one fourth of the height of the muffle chamber. Inaccordance with another, and particularly preferable embodiment of theinvention, the exhaust and injection openings are located at a distancefrom the bottom wall of the muffle chamber that corresponds to abouthalf the height of the muffle chamber.

Another advantage of the baking and roasting oven stems from thedisposition of both the exhaust and injection openings at the same levelof the mufi'le chamber so that the flow of circulating hot air is in asubstantially horizontal direction and thereby primarily comes intocontact with the side walls of the muffle chamber and heats them. Theinvention is therefore used to particular advantage in such baking androasting ovens that are provided with an upper" and lower heat for thetop and bottom walls, respectively, of the muffle chamber. When aself-cleaning operation is carried out, the muffle chamber is heatedlargely to' thermal balance or equilibrium so that more rapid heating ispossible than with the heretofore known selfcleaning ovens operatingwithout blowers.

In accordance with yet another feature of the invention, the exhaust andinjection openings are located in the rear wall of the muffle chamber.The side walls of the muffle chamber are effectively heated when, inaccordance with the invention, the mutual spacing of the exhaust and theinjection openings is equal to at least half the width of the rear wall.The heating device of the baking and roasting oven then heats the sidewalls of the muffle chamber by means of the circulating blower, and thetop and bottom walls are heated by the upper and lower heat". Bydisposing the exhaust and injection openings in the rear wall of themuffle chamber, it is also possible to guide the horizontally directedflow of the circulated hot air to the inner surface of the door of thebaking and roasting oven that is located on the side of the mufflechamber which is op- I which:

posite the rear wall of the muffle chamber. The circulated hot air thenalso ensures a thorough cleaning of the inner surface of the door.

Locating the exhaust and injection openings nects the exhaust andinjection openings, assumesa horizontal position,- in accordance withthe invention. i The blower channel is disposed parallel to zones ofequal temperature, because any heat gradient, which may, on occasion,occur through the wall of the muffle chamber, is noticeably strongest invertical direction. Therefore, in the bakingand roasting oven of theinvention, no significant temperature differences and consequentexpansion differences, which can cause thermal stresses, will occurbetween the blower channel and the wall of the baking and roasting oven.Total protection against thermal stresses can be attained if, inaccordance with an additional feature of the invention, the blowerchannel is fioatingly or yieldably mounted with respect to the wall ofthe muffle chamber.

Other features which are considered as characteristic for the inventionare set forth in the-appended claims.

Although the invention is illustrated and described herein "as embodiedin baking and roasting oven, it is nevertheless not intended to belimited to the details shown,. since various modifications andstructural advantages thereof w'ill' be best understood from thefollowing description of specific embodiments when read in connectionwith the accompanying drawing, in

v FIG. 1 is a perspective view of the muffle chamber of a baking androasting oven showing a blower channel mounted on the rear wall thereofand having a blower and a heating member installed therein;

FIG. 2 is an enlarged elevational view of the rear wall of the-mufflechamber surmounted by the blower channel shown in FIG. 1;

. FIG. 3' is a cross-sectional view of FIG.2,tak en along the line HIIII in the direction of the arrows;

FIG. 4 is a sectional view of FIG. 2, taken along the I line IV IV, inthe direction of the arrows;

.FIGS. 5 and 6 are'enlarged plan and sectional views, respectively, ofone of the perforated 'dis cs inserted into the rear wall of the mufflechamber as shown in FIG. 2;

and

FIGS. 7 and 8 are views similar to FIGS. 5 and 6, respectively, of amodified form of the perforated disc.

Referring now to the drawings, and first particularly to FIGS. 1 and 4thereof, there is shown therein a rear wall 1 of a muflle or mufflechamber 100 of a baking. and roasting oven, on which there is mounted,at about half the height of the muffle chamber, a blower channel or duct2 which interconnects an exhaust or suction fanwheel blower or impeller6, the hollow profile member having a rectangular cross section. Inparticular, the blower channel is formed of two similar wall portions 8which are mutually displaced and spotopenings 9 that are adjusted oraccommodated to. the

exhaust and injection openings 3 and .4, respectively, and, in the wallportion 8 facing away from the rear wall 1, entry openings 10 areprovided for the fanwheel blower 6 and for heating member 5 (FIG. 3).

The rear wall 1 and the blower duct or channel 2 are connected by screws11, which pass centrally through the wall portion 8 of the blowerchannel or duct 2 that faces the rear wall 1 of the muffle chamber 100,as well as centrally through perforated discs 12 which cover the exhaustand injection openings 2 and are located at the inner surface of therear wall 1. The perforated discs 12 are inserted in stampings 13 formedin the rear wall 1 and having edges which surround the perforated discs12 with clearance. The blower channel or duct 2 is mounted so as to bespaced from the rear wall 1, annular seals 14 of heat damming orinsulating material being disposed therebetween. The annular seals 14are inserted into depressions 15 formed in the wall portion 8 that facesthe rear wall 1.

The entry openings 10 formed in the wall portion 8 of the blower channelor duct 2 faces away from the rearwall l of the muffle chamber 100, arecovered by flange plates 16 and '17 thatare' provided on their interiorside, with a heat-damming or insulating lining 18 and 19, respectively.The flange plate 16 is carrier of g the bearing 20 for the shaft 21 ofthe fanwheel blower 6. The flange'plate 1'6 and the thermally insulatinglinblower channel or duct 2 with respect to the rear wall 1 of themuffle chamber 100. The perforated discs 12' serve as holding membersproper for the blower channel or duct 2 at the rear wall 1 and arefastened by screws 11 to the blower channel or duct 2. The stampings 13formed in the rear wall 1 surround the perforated discs 12 with suchclearance that the blower channel or duct 2 with the perforated disc 12has a predetermined freedom of movement with respect to rear wall 1.Preferably, the tightening force exerted by the screws 11 will beadjusted so that the blower channel or duct 2 is pressed against theannular seals 14 with adequate holding force, yet permitting, on theother hand, adjustment or compensation for any diflerences in thermalexpansion that may occur between the blower channel or duct 2 and therear wall 1. It is advantageous for the annular seals 14 to be formed,for example, of graphitized asbestos material, which has a beneficialeffect upon the length adjustment or equalization due to theslideability thereof.

The mutual spacing between the exhaust and injection inlet openings 3and 4, respectively, formed in the rear wall 1 of the muffle chamber 100has been selected at a maximum, in the illustrated embodiment, takinginto consideration the dimension of the blower channel or duct 2. Theexhaust and injection openings 3 and 4, thus become positioned intriangular fields 25 of the rear wall 1, which are defined by thestamping edges 26 formed in the rear wall 1. This disposition of theexhaust and injection openings 3 and 4 insures that theside walls of themuffle 100, as well as a non-illustrated door which closes the frontside of the muffle 100, are swept over by the circulated hot air flowand adequately heated. The stamping edges 26 define, together withanother stamping edge 27, two additional trapezoidal fields 28 which areinclined at a flat or obtuse angle toward one another and toward thefields 25.

The camber or curvature of the rear wall which is thereby produced isadvantageous with respect to the thermal expansion characteristics ofthe rear wall 1,

opening 4 so that it travels at an angle to the axis of the guide disc29. This possible deflection of the hot air is advantageous when thereis a need to have the hot air blow against specific parts of the innerwall surface of the muffle chamber 100, and can, moreover, be used alsoby properly 10 equipping the exhaust opening 3 for the hot airdischarging from the muffle chamber 100.

.The use of the guide discs 29 is not limited to selfcleaning operationsbut is also especially suitable for carrying out baking and roastingoperations by means of circulated hot air.

It is advantageous that the guide disc 29 be mounted so that they arepivotable with respect to the rear wall 1 and that they be provided withan adjusting handle, in a the guide discs 29 can then be adjusted in arelatively simple manner to therespective' operational requirements.

I claim:

1. Baking and roasting oven including a muffle chamber having a topwall, a bottom wall and a lateral wall extending between the top andbottom walls, comprising a heating means including a circulating blowerfor hot air, a blower channel for the hot air circulated by said blower,said blower channel interconnecting respective hot air exhaust 'and hotair injection openings formed in the lateral wall of the muffle chamber,said exhaust and injection openings being at an elevation of at leastone-fourth the height of the muffle chamber from the bottom wall and thetop wall thereof.

2. Baking and roasting oven according to claim 1 wherein said exhaustand injection openings are located at the same level of the mufflechamber.

3. Baking and roasting oven according to claim 2 wherein said exhaustopening and said injection opening are mutually spaced apart a distancecorresponding to at least half the width of the rear wall.

6. Baking and roasting oven according to claim 1 wherein said blowerchannel is floatingly mounted with respect to the lateral wall of themuffle chamber.

7. Baking and roasting oven according to claim 1 in-- cluding annularseals of heat-damming material disposed coaxially to said exhaust andinjection openings, said blower channel being mounted spaced from thelateral wall of the muffle chamber, said annular seals beinginterspersed between the lateral wall and the blower channel.

8. Baking and roasting oven according to claim 7 wherein the lateralwall of the muffle chamber is formed with depressions, and said annularseals are received in said depressions.

9. Baking and roasting oven according to claim 7 wherein said blowerchannel is formed with depressions, and said annular seals are receivedin said depressions.

10. Baking and roasting oven according to claim 1 wherein said blowerchannel is formed of a hollow profile member closed at the ends thereofand containing a heating member and a fanwheel blower therein.

11. Baking and roasting oven according to claim 10 wherein said hollowprofile member has a rectangular cross section.

12. Baking and roasting oven according to claim 1 including perforateddiscs covering said exhaust and injection openings, respectively, saidperforated discs being located at the inner side of the muffle chamberand being fastened by central screws to said blower channel.

13. Baking and roasting oven according to claim 12 wherein the lateralwall of the muffle chamber is formed with stampings wherein saidperforated discs are received, said stampings having an edge surroundingthe respective perforated discs with clearance.

14. Baking and roasting oven according to claim 12 wherein saidperforated discs are formed as guide discs having means for deflectinghot air exhausting from said exhaust opening so that it travels at anangle to the fle chamber, said blower channel side being formed withpassages accommodated to said exhaust and injection openings.

l9. Baking and roasting oven according to claim 18 wherein said blowerchannel has a side facing away from the muffle chamber, said latter sidebeing formed with inlet openings disposed oppositesaid passages andadapted to accommodate therein a fanwheel blower and a heatingmember,respectively.

20. Baking and roasting oven according toclaim l9

1. Baking and roasting oven including a muffle chamber having a topwall, a bottom wall and a lateral wall extending between the top andbottom walls, comprising a heating means including a circulating blowerfor hot air, a blower channel for the hot air circulated by said blower,said blower channel interconnecting respective hot air exhaust and hotair injection openings formed in the lateral wall of the muffle chamber,said exhaust and injection openings being at an elevation of at leastone-fourth the height of the muffle chamber from the bottom wall and thetop wall thereof.
 2. Baking and roasting oven according to claim 1wherein said exhaust and injection openings are located at the samelevel of the muffle chamber.
 3. Baking and roasting oven according toclaim 2 wherein said exhaust and injection openings are located at anelevation one half the height of the muffle chamber.
 4. Baking androasting oven according to claim 1 wherein lateral wall of the mufflechamber is the rear wall thereof, and said exhaust and injectionopenings are formed in the rear wall.
 5. Baking and roasting ovenaccording to claim 4 wherein said exhaust opening and said injectionopening are mutually spaced apart a distance corresponding to at leasthalf the width of the rear wall.
 6. Baking and roasting oven accordingto claim 1 wherein said blower channel is floatingly mounted withrespect to the lateral wall of the muffle chamber.
 7. Baking androasting oven according to claim 1 including annular seals ofheat-damming material disposed coaxially to said exhaust and injectionopenings, said blower channel being mounted spaced from the lateral wallof the muffle chamber, said annular seals being interspersed between thelateral wall and the blower channel.
 8. Baking and roasting ovenaccording to claim 7 wherein the lateral wall of the muffle chamber isformed with depressions, and said annular seals are received in saiddepressions.
 9. Baking and roasting oven according to claim 7 whereinsaid blower channel is formed with depressions, and said annular sealsare received in said depressions.
 10. Baking and roasting oven accordingto claim 1 wherein said blower channel is formed of a hollow profilemember closed at the ends thereof and containing a heating member and afanwheel blower therein.
 11. Baking and roasting oven according to claim10 wherein said hollow profile member has a rectangular cross section.12. Baking and roasting oven according to claim 1 including perforateddiscs covering said exhaust and injection openings, respectively, saidperforated discs being located at the inner side of the muffle chamberand being fastened by central screws to said blower channel.
 13. Bakingand roasting oven according to claim 12 wherein the lateral wall of themuffle chamber is formed with stampings wherein said Perforated discsare received, said stampings having an edge surrounding the respectiveperforated discs with clearance.
 14. Baking and roasting oven accordingto claim 12 wherein said perforated discs are formed as guide discshaving means for deflecting hot air exhausting from said exhaust openingso that it travels at an angle to the axis of the guide discs. 15.Baking and roasting oven according to claim 14 wherein said guide discsare mounted so as to be pivotable relative to the lateral wall of themuffle chamber.
 16. Baking and roasting oven according to claim 15wherein said guide discs have a screen-type raster with inclinedlamellae.
 17. Baking and roasting oven according to claim 14 whereinsaid guide discs have a respective adjusting handle.
 18. Baking androasting oven according to claim 1 wherein said blower channel has aside facing the muffle chamber, said blower channel side being formedwith passages accommodated to said exhaust and injection openings. 19.Baking and roasting oven according to claim 18 wherein said blowerchannel has a side facing away from the muffle chamber, said latter sidebeing formed with inlet openings disposed opposite said passages andadapted to accommodate therein a fanwheel blower and a heating member,respectively.
 20. Baking and roasting oven according to claim 19including flange plates covering said inlet openings, said flange plateshaving a lining of heat-damming material on the side thereof facing saidinlet openings.
 21. Baking and roasting oven according to claim 20including respective bearing means for said fanwheel blower and saidheating member, said flange plates serving as carriers for therespective bearing means.